LibGUI: Use UndoStack::on_state_change inside TextDocument/TextEditor

Have TextDocument listen for state changes on the internal undo stack,
and forward those to all clients via a new virtual function.

This simplifies updating the can_undo / can_redo states of TextEditor.

1 files changed, 1 insertions, 0 deletions

diff --git a/Userland/Libraries/LibGUI/TextDocument.h b/Userland/Libraries/LibGUI/TextDocument.h
index fa1b7beeef..aac61254fb 100644
--- a/Userland/Libraries/LibGUI/TextDocument.h
+++ b/Userland/Libraries/LibGUI/TextDocument.h
@@ -47,6 +47,7 @@ public:
         virtual void document_did_change() = 0;
         virtual void document_did_set_text() = 0;
         virtual void document_did_set_cursor(const TextPosition&) = 0;
+        virtual void document_did_update_undo_stack() = 0;
 
         virtual bool is_automatic_indentation_enabled() const = 0;
         virtual int soft_tab_width() const = 0;